This invention relates to a data transmission method and a data transmission apparatus by which an audio information signal is transmitted with a new data signal superposed thereon and a data reception method and a data reception apparatus by which an audio information signal with a new data signal superposed thereon is received and demodulated.
When it is tried to perform timer reservation of a program on a conventional television set, a video tape recorder (VTR) or a like apparatus, a channel name, a reservation date, a reservation time and so forth are set first, and then an execution button is operated. Alternatively, a code determined so as to designate a program is inputted and an execution key is operated to effect timer reservation.
In order to eliminate such a complicated procedure for reservation operation, it is a possible idea to transmit program information in a superposed relationship together with a video signal or an audio signal so as to be used for a reservation procedure. Where such information to be noticed by users is sent, there is a problem in that it is required to send data and cause a receiving apparatus to generate chimes or musical sound separately.
Further, where data are superposed on an audio signal, since the frequency of the audio signal is in a voice band which can be recognized by users, there is another problem in that the sound reproduced based on the audio signal sounds disagreeable to a user because of sound arising from the data superposed on the audio signal.
While it is possible to send a video signal with data superposed thereon, in this instance, the data may possibly be interposed in a horizontal retrace line interval or a vertical retrace line interval of a vertical blanking interval or the like. However, while such interposition of data allows superposition of the data without having any bad influence on a video signal or an audio signal, this requires the supplier side of a source such as a broadcasting station or a repeating station for provision of an apparatus called inserter which is comparatively complicated and expensive.
Further, where data are superposed on a video signal, since the frequency band of the video signal is broad, an excessively high transmission capacity is required, and effective utilization of a transmission line cannot sometimes be anticipated in that the efficiency with regard to data is deteriorated and so forth.